Organic peroxides derived from unsaturated compounds

ABSTRACT

New organic peroxides having the formula ##EQU1## may be prepared by reacting a monohydroperoxide selected from R 5  OOH and R 6  OOH with an unsaturated carbonyl compound having the formula ##EQU2## the reaction being carried out in the presence of an acid catalyst at a temperature between about -30°C and +80°C, the molar ratio of the carbonyl compound to the hydroperoxide being between about 1:2 and 1:10. The new organic peroxides are particularly useful for crosslinking plastomers, vulcanizing elastomers, and as initiators for radical polymerizations.

This a continuation of application Ser. No. 53,267, filed July 8, 1970 now U.S. Pat. No. 3,896,176.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to new organic peroxides and more particularly to new organic peroxides which have a double peroxidic function and are derived from unsaturated compounds, as well as to the use of these new organic peroxides in the crosslinking of plastomers, in the vulcanization of elastomers and as organic reactants.

2. Description of the Prior Art

Organic peroxides are used as initiators for radical polymerization, vulcanizing agents for elastomers, and cross-linking agents for thermoplastic polymers. A discussion of typical organic peroxides used in the prior art, their preparation, and some difficulties associated with the preparation and use of some prior art peroxides appears in U.S. Pat. No. 3,489,730, which was issued Jan. 13, 1970, to the assignee hereof and the contents of which are hereby incorporated herein by reference.

The present invention provides a particular class of new organic peroxides having good stability and low volatility, which peroxides are particularly suited and interesting both as cross-linking agents for plastomers and as vulcanizing agents for elastomers.

SUMMARY OF THE INVENTION

The present invention provides a new series of peroxides with a double peroxidic function characterized by one or more unsaturated bonds and having the general formula: ##EQU3## wherein R₁ is selected from the group consisting of unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-30 C; unsubstituted, alkyl substituted, hydroxy substituted and halogen substituted phenyl radicals having 6-26 C; and unsubstituted, alkyl substituted and halogen substituted heterocyclic radicals having 4-15 C; R₂ is selected from the group consisting of hydrogen, alklyl radicals having 1-12 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-20 C halogen substituted alkyl radicals having 1-12 C; and unsubstituted, alkyl substituted and haloen substituted phenyl radicals; and R₁ and R₂ together with the carbon atom to which they are bonded may form a cycloaliphatic ring selected from the group consisting of unsubstituted and alkyl, phenyl, phenylalkyl, alkylidene and phenylalkylidene substituted cycloaliphatic rings having 5-30 C; R₃ and R₄ are each selected from the group consisting of hydrogen, alkyl radicals having 1-12 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-20 C; unsubstituted, alkyl substituted and halogen substituted phenyl radicals having 6-20 C; halogen substituted alkyl radicals having 1-12 C, and halogen substituted phenylalkyl radicals having 7-20 C; and R₃ and R₄ taken together with the two adjacent carbon atoms to which they are respectively bonded may form a cycloaliphatic ring selected from the group consisting of unsubstituted and alkyl, phenyl, phenylalkyl, alkylidene, phenylalkylidene and hydroxy phenylalkylidene substituted cycloaliphatic rings having 5-25 C; R₅ and R₆ are each selected from the group consisting of alkyl radicals having 4-12 C, phenylalkyl radicals having 9-18 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-21 C; unsubstituted, alklyl substituted and halogen substituted phenylcycloalkyl radicals having 9-25 C; halogen substituted alkyl radicals having 4-12 C, and halogen substituted phenylalkyl radicals having 9-18 C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Tertiary alkyl groups, for example, ter.-butyl, ter.-amyl and cumyl, are preferred as the R₅ and R₆ radicals.

Examples of compounds of the present invention, within the above general formula, include:

a. 1-phenyl-3,3-di(ter.-butyl-peroxy)-propene-1;

b. 1-phenyl-3,3-di(cumyl-peroxy)-propane-1;

c. 1-phenyl-3,3-di(ter.butyl-peroxy)-butene-1;

d. 1-phenyl-3,3-di(cumyl-peroxy)-butene-1;

e. 1-phenyl-3-ter.-butyl-peroxy-3-cumyl-peroxy-butene-1;

f. 1-cyclohexylidene-2,2-di(ter.-butyl-peroxy)-ethane;

g. 1-furyl-3,3-di(ter.-butyl-peroxy)-propene-1;

h. 1-furyl-2-methyl-3,3-di(ter.-butyl-peroxy)-propene-1;

i. 1,1di(ter.-butyl-peroxy)-2-benzylidene-cyclohexane;

l. 1,1-di(ter.-butyl-peroxy)-2,6-di(4-hydroxy-benzylidene)cyclohexane; and

m. 1,1-di(ter.-butyl-peroxy)-2,6-di(4-isopropyl-benzylidene)cyclohexane;

n. 1-cyclohexyl-3,3-di(ter.-butyl-peroxy)-butene-1;

o. 2,3-di(phenyl)-4-di(ter-butyl-peroxy)-butene-2;

p. 1-phenyl-3,3-di(cyclohexen-2-yl-1-peroxy)propene-1;

q. 1-phenyl-3,3-di(cyclohexen-2-yl-1-ethyl-peroxy)propene-1;

r. 1-phenyl-3,3-di(tetralin-1-peroxy)propene-1;

s. 1-phenyl-3,3-di(tetralin-1-methyl-1-peroxy)propene-1.

The diperoxides of this invention have the unusual properties of having good stability and low volatility at temperatures higher than room temperature. These properties permit the compounds to be incorporated in plastomers as crosslinking agents and in saturated elastomers as vulcanizing agents without giving rise to the troublesome secondary phenomena (for instance prevulcanization and pre-crosslinking) which arise when using less stable, more volatile, prior art peroxides.

In accordance with a preferred embodiment, the diperoxides of the invention may be prepared by reacting an unsaturated carbonyl derivative, dissolved in a suitable solvent, with an organic hydroperoxide in the presence of an acid catalyst at a temperature between about -30° and +80°C, preferably between about -10° and +50°C.

The unsaturated carbonyl compounds which may be used in the foregoing reaction have the general formula ##EQU4## wherein R₁, R₂, R₃ and R₄ are as defined above. Examples of such carbonyl compounds include, for instance, cinnamic aldehyde, furyl-acrylic aldehyde, alpha-cyclo-hexylidene-acetaldehyde, alphabenzylidene-acetone and 2,6-benzylidene-cyclohexanone.

The hydroperoxides which may be used in the reaction have the general formula R-OOH wherein R represents R₅ and R₆ as defined above. Examples of such compounds include: ter.-butyl hydroperoxide, and substituted derivatives thereof; cumyl-hydroperoxide and substituted derivatives thereof; 1,3-diisopropylbenzene-α -monohydroperoxide and 1,4 diiso-propylbenzene-α-monohydroperoxide; 1-methyl-cyclohexyl-hydroperoxide; 2-methyl-2-hydroperoxy-butyn-3; 1-menthane-hydroperoxide; and 1-phenyl-cyclohexyl hydroperoxide.

The solvents which may be employed in the reaction include for example, linear aliphatic hydrocarbons having 6 to 10 C, linear aliphatic halogenated hydrocarbons having 1 or 2 C and from 1 to 4 Cl aromatic hydrocarbons, having from 6 to 9 C, which may be halogenated with 1 or 2 Cl, cycloaliphatic hydrocarbons having 6 to 10 C, and ethers, for instance ethylether.

The molar ratio of unsaturated carbonyl compound to hydroperoxide is between about 1:2 and 1:10, preferably between about 1:2.5 and 1:5.

The catalysts used are preferably sulfonic acids, such as for instance, para-toluene sulphonic acid.

The new diperoxides of the present invention are soluble in chlorinated and unchlorinated aliphatic and aromatic hydrocarbon solvents, and in aliphatic esters. A particular feature of this invention is that the diperoxides of this invention are excellent crosslinking agents for plastomers, vulcanizing agents for elastomers and initiators for radical polymerization. The use of the diperoxides defined above for the crosslinking of plastomers is particularly applicable to the polyolefins and more particularly to polyethylene.

The crosslinking of polyethylene with the peroxides of the present invention results in a product having improved mechanical properties at high temperatures, reduced fragility at low temperatures and reduced solubility in aliphatic and aromatic hydrocarbons, even chlorinated ones. Furthermore, the crosslinked polyethylene has increased resistance to light, weather and to ageing.

The crosslinking is carried out in accordance with this aspect of the present invention at a temperature between about 100° and 200°C, preferably between about 145° and 165°C, at a pressure between about 50 and 200 kg/cm² and for periods of from about 5 to 60 minutes, preferably from about 10 to 30 minutes. The concentration of the peroxide is between about 0.5 and 10% by weight, preferably between about 2 and 5% by weight, based on the weight of the plastomer.

The vulcanization of elastomers, for example, ethylene/propylene copolymers, in accordance with the present invention may be carried out at a temperature between about 140° and 190°C. preferably between about 150° and 170°C, for periods of from about 5 to 20 minutes, preferably between about 5 to 15 minutes. The cocentration of the peroxide is between about 0.5 and 10% by weight, preferably between about 2 and 5% by weight, based on the weight of the elastomer.

Particularly suitable vulcanization mixes for vulcanizing ethylene/propylene copolymer have compositions within the following ranges:

    ______________________________________                                         ethylene/propylene copolymer                                                                    100        parts by weight                                    carbon black     20 to 80   parts by weight                                    ZnO              1 to 10    parts by weight                                    sulfur           0.15 to 0.5                                                                               parts by weight                                    peroxide         0.005 to 0.02                                                                             moles.                                             ______________________________________                                    

The most notable advantages afforded by the use of the diperoxides of the present invention in the crosslinking of plastomers and in the vulcanization of saturated elastomers include: practically odorless crosslinked and vulcanized products; absence of "blooming" phenomena; short vulcanization times and low vulcanization temperatures; the greater effectiveness of the new diperoxides remains unaltered even in the presence of known fillers, reinforcing agents (for instance carbon black, Mg hydrosilicate), additives of the type ageing resistant plastified and homogenized masses can be obtained without pre-crosslinking or pre-vulcanization phenomena which hinder the further processing.

The possibility of obtaining plastified and homogenized masses without pre-crosslinking or pre-vulcanization phenomena is due to the fact that the peroxides do not thermally decompose to the mixing temperature giving rise to the beginning of the pre-crosslinking and pre-vulcanization phenomena.

The following examples are presented to further illustrate the present invention.

EXAMPLE 1

200 g of anhydrous benzene and 131.5 g of 80% ter-butyl hydroperoxide were introduced into a flask at ambient temperature provided with a stirrer. The temperature was then increased to 40°C and, during 10 minutes, there were simultaneously added 51.6 g of 98% cinnamic aldehyde and 100 g of a benzene/methanol solution of paratoluenesulfonic acid, havin the following composition by weight:

0.14% of paratoluenesulfonic acid, 1.42% of anhydrous methanol, and 98.44% of anhydrous benzene.

The mixture was then stirred for 3 hours at 40°C. Thereafter, the organic solution was washed with 8% aqueous solution of NaHCO₃, then with 5% aqueous NaOH, and finally wit water to a pH of 6.5.

The solvent was then removed under vacuum (final pressure, 0.2 mm Hg) at 30°C, obtaining 92 g of a white crystalline product as residue.

After repeated recrystallizations from methanol, there were obtained 75 g of a solid crystalline product which was identified as 1-phenyl-3,3-di(ter.-butyl-peroxy)-propene-1. This product had product had the following characteristics:

    ______________________________________                                         melting point              58-59°C                                      iodometric liter:          98%                                                 decomposition temperature: 118°C                                        half life at 120°C  30 minutes                                          carbon content, weight % found:                                                                           69.0                                                carbon content, weight % calculated:                                                                      69.36                                               hydrogen content, weight % found:                                                                          9.1                                                hydrogen content, weight % calculated:                                                                     8.90.                                              ______________________________________                                    

EXAMPLE 2

200 g of normal hexane and 120 g of 90% ter.-butyl hydroperoxide were introduced into a flask at ambient temperature provided with a stirrer. The temperature was increased to 42° to 45°C and, during 10 minutes, there were simultaneously introduced 48.8 g. of distilled furyl-acrylic aldehyde and 160 g of a benzene/methanol solution of paratoluenesulfonic acid having the following composition by weight:

1.42% of anhydrous methanol, 98.44% of anhydrous benzene and 0.14% of paratoluenesulfonic acid, i.e., the same composition as the solution employed in Example 1.

This mixture was then stirred for 3 hours and 30 minutes at a temperature of 42° to 45°C. The organic solution was then washed with water, with an 8% NaHCO₃ solution and then again with water to a pH of 6.5. The solvent was removed under vacuum at 40°C, with a final pressure of 0.2 mmHg.

The solid residue (119 g) was crystallized from methanol and there were thus obtained 101 g of a light yellow crystalline product which was identified as 1-furyl-3,3-di(ter.butyl-peroxy)-propene-1.

The product had the following characteristics:

    ______________________________________                                         melting point:             56-57°C                                      iodometric liter:          99.5%                                               decomposition temperature: 104°C                                        half life at 118°C: 30 minutes                                          carbon content, weight % found:                                                                           64.0%                                               carbon content, weight % calculated:                                                                      63.36%                                              hydrogen content, weight % found:                                                                          8.7%                                               hydrogen content, weight % calculated:                                                                     8.51%.                                             ______________________________________                                    

EXAMPLE 3

50 cc of benzene and 14.5 g. of 83.8% cumene hydroperoxide were introduced into a flask at ambient temperature provided with a stirrer. The temperature of the solution was then increased to 42° to 45°C. Then, during 15 minutes, there were simultaneously added, dropwise, a mixture consisting of 5.1 g of 98.2% cinnamic aldehyde and 20 g of a solution of paratoluenesulfonic acid having the following composition by weight: 0.2% of paratoluenesulfonic acid, 1.4% of absolute ethyl alcohol and 98.4% of benzene.

This mixture was then stirred for 3 hours at 45°C, and at the end of this time it was washed with water, then with a 5% NaHCO₃ solution, then with 5% NaOH, and finally with water until neutral pH. The solvent was then distilled under vacuum at 30° to 32°C, thereby obtaining 14 g of an oily yellow product identified as 1-phenyl-3,3-di(cumyl-peroxy)-propene-1. This product showed the following characteristics:

    ______________________________________                                         iodometric titration:      77.6%                                               n.sub.D.sup.20 :           1.5586                                              decomposition temperature: 125°C                                        half life at 119°C: 30 minutes                                          carbon content, weight % found:                                                                           77.0%                                               carbon content, weight % calculated:                                                                      77.4%                                               hydrogen content, weight % found:                                                                          7.3%                                               hydrogen content, weight % calculated:                                                                     7.22%                                              ______________________________________                                    

EXAMPLE 4 Vulcanization

The vulcanization tests were carried out on mixes of an ethylene/propylene copolymer, having a molar ratio ethylene/propylene 50/50 and a viscosity Mooney ML(1+1) 100°C = 35. In Table 1 there are compared the vulcanization rates determined on equivalent mixes containing as peroxides, respectively, 1-phenyl-3,3-di(ter.-butyl-peroxy)-propene-1; 1-furyl-3,3-di(ter.-butyl-peroxy)-propene-1 and dicumyl peroxide.

The vulcanization rate was determined at 177°C on a Monsanto TM-10 rheometer. The mixes used had the following composition:

    ______________________________________                                         ethylene/propylene copolymer                                                                     100     parts by weight                                      carbon black      50      parts by weight                                      ZnO               3       parts by weight                                      sulfur            0.32    parts by weight                                      peroxide          0.01    moles.                                               ______________________________________                                    

                                      TABLE 1                                      __________________________________________________________________________     Vulcanization rate                                                                                  Parts per 100 g of ethy-                                                                     Vulcanization                                                                          Vulcanization                                            lene/propylene copolymer                                                                     temperature                                                                            time                                Peroxide             g      moles  °C                                                                              minutes                             __________________________________________________________________________             OOC(CH.sub.3).sub.3                                                            CH=CH--CH∠                                                                            2.94   0.01   177     6                                           OOC(CR.sub.3).sub.3                                                            OOC(CH.sub.3).sub.3                                                            CH=CH--CH∠                                                                            2.84   0.01   177     5                                           OOC(CH.sub.3).sub.3                                                            Dicumylperoxide                                                                             2.70   0.01   177     14                                  __________________________________________________________________________

Table 2 compares the physical properties of the vulcanized products obtained by the use of 1-phenyl-3,3-di(ter.-butyl-peroxy)-propene-1; and 1-furyl-3,3-di(ter.-butyl-peroxy)-propene-1, at vulcanization times between 5 and 60 minutes, at a vulcanization temperature of 150°C, with those of the vulcanized products obtained using dicumyl peroxide at 165°C for 30 minutes (these being the optimal conditions for dicumyl peroxide).

From the results set forth in Table 2 it appears evident that the peroxides of the present invention permit the use of a low vulcanization temperature while affording high vulcanization rates and better physical characteristics of the vulcanized product than those obtained by using dicumylperoxide at higher temperatures (165°C) for longer periods of time (30 minutes).

                                      Table 2                                      __________________________________________________________________________                              Vulcanization                                                                           Physical Properties of the Vulcanized                                          Products                                                       Parts per                                                                      100 parts                Modulus                                                                             Modulus                                                                             Modulus                                     of ethylene/                                                                          Temp-         Elonga-                                                                            at 100%                                                                             at 200%                                                                             at 300%                                     propylene                                                                             era-     Tensile                                                                             tion at                                                                            Elonga-                                                                             Elonga-                                                                             Elonga-                   Peroxide          copolymer                                                                             ture                                                                               Time strength                                                                            break                                                                              tion tion tion RHD                  __________________________________________________________________________                       moles  °C                                                                          minutes                                                                             kg/cm.sup.2                                                                         %   kg/cm.sup.2                                                                         kg/cm.sup.2                                                                         kg/cm.sup.2                                                                         hardness             __________________________________________________________________________     OOC(CH.sub.3).sub.3                                                                              0.015                                                                              4.41                                                                              150  5   215  550 20   43   92   63                   CH=CH--CH∠∠      10   218  460 25   66   127  65                   OOC(CH.sub.3).sub.3          15   192  370 24   67   137  65                                                30   208  400 25   71   138  65                                                60   192  400 25   65   133  65-66                OOC(CH.sub.3).sub.3                                                                              0.010                                                                              3.41                                                                              150  5   134  350 26   60   106  66                   CH=CH--CH∠             10   145  390 27   60   104  66                   OOC(CH.sub.3).sub.3          15   149  400 25   57   102  66                                                30   125  320 25   59   106  66                                                60   136  360 25   62   109  65                   Dicumylperoxide   0.010                                                                              2.70                                                                              165 30   180  410 21   58   119  68                   __________________________________________________________________________

EXAMPLE 5 Crosslinking

The crosslinking tests were carried out on mixes of low-density (0.918) polyethylene and peroxide. Table 3 sets forth the physical properties of the polyethylene crosslinked by using, respectively, the diperoxides prepared in Example 1 (1-phenyl-3,3-di(ter.-butyl-peroxy)-propene-1), Example 2 (1-furyl-3,3-di(ter.-butyl-peroxy)-propene-1), and a known diperoxide (dicumylperoxide).

The results thus obtained show the excellent crosslinking activity of the diperoxides of the invention.

                                      Table 3                                      __________________________________________________________________________                       Moles of                                                                       peroxide                                                                              Crosslinking                                                                            Physical Characteristics                                       in 100 g    Temp-        Elonga-                                                                             Degree of swell-                                 of          era Yield                                                                              Tensile                                                                             tion at                                                                             ing in xylol at                Peroxide          polyethylene                                                                          Time ture                                                                               point                                                                              strength                                                                            break                                                                               80°C for 21 hours                                minutes                                                                             °C                                                                          kg/cm.sup.2                                                                        kg/cmk.sup.2                                                                        in %                                __________________________________________________________________________     None              --     20   145 57.8                                                                                73  150  soluble                        OOC(CH.sub.3).sub.3                                                            C.sub.6 H.sub.5 --CH=CH--CH∠                                                               0.01   20   145 52  150  240  10.4                           OOC(CH.sub.3).sub.3                                                            OOC(CH.sub.3).sub.3                                                            CH=CH--CH∠  0.01   20   145 57  140  400  14                             OOC(CH.sub.3).sub.3                                                            Dicumylperoxide   0.01   20   145 52.9                                                                               132  456  21.3                           __________________________________________________________________________

The determination of the degree of swelling was carried out on the crosslinked product. By the term "degree of swelling" is meant the volume of solvent absorbed by a given volume of crosslinked polyethylene. The test method consists of suspending a small basket containing a plate of about 0.2 g. of crosslinked polyethylene in a test tube containing 100 cc of xylene stabilized with 0.1 g of phenolic antioxidant, i.e., 4,4-thio-bis(3-methyl-6-ter.-butyl-phenol). The operation is carried out at 80°C for 21 hours. The degree of swelling is given by the following formula: ##EQU5## wherein a = weight of the test sample after 21 hours at 80°C in xylene, b = weight of test sample before the test, c = weight of test sample after drying at the end of the test, ##EQU6##

Variations can, of course, be made without departing from the spirit and scope of the invention. 

Having thus described our invention, what we desire to secure by Letters Patent and hereby claim is:
 1. A vulcanizable composition comprising an elastomer and an organic peroxide having the formula: ##EQU7## wherein R₁ is selected from the group consisting of unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-30 C; unsubstituted, alkyl substituted, hydroxy substituted and halogen substituted phenyl radicals having 6-26 C; and unsubstituted, alkyl substituted and halogen substituted heterocyclic radicals having 4-15 C; R₂ is selected from the group consisting of hydrogen, alkyl radicals having 1-12 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-20 C, halogen substituted alkyl radical having 1-12 C; and unsubstituted, alkyl substituted and halogen substituted phenyl radicals; and R₁ and R₂ together with the carbon atom to which they are bonded may form a cycloaliphatic ring selected from the group consisting of unsubstituted and alkyl, phenyl, phenylalkyl, alkylidene and phenylalkylidene substituted cycloaliphatic rings having 5-30 C; R₃ and R₄ are each selected from the group consisting of hydrogen, alkyl radicals having 1-12 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-20 C; unsubstituted, alkyl substituted and halogen substituted phenyl radicals having 6-20 C; halogen substituted alkyl radicals having 1-12 C, and halogen substituted phenylalkyl radicals having 7-20 C; and R₃ and R₄ taken together with the two adjacent carbon atoms to which they are respectively bonded may form a cycloaliphatic ring selected from the group consisting of unsubstituted and alkyl, phenyl, phenylalkyl, alkylidene, phenylalkylidene and hydroxy phenyalkylidene substituted cycloaliphatic rings having 5-25 C; R₅ and R₆ are each selected from the group consisting of alkyl radicals having 4-12 C, phenylalkyl radicals having 9-18 C; unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-21 C; unsubstituted, alkyl substituted and halogen substituted phenylcycloalkyl radicals having 9-25 C; halogen substituted alkyl radicals having 4-12 C, and halogen substituted phenylalkyl radicals having 9-18 C.
 2. A crosslinkable composition comprising a plastomer and an organic peroxide having the formula: ##EQU8## wherein R₁ is selected from the group consisting of unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-30 C; unsubstituted, alkyl substituted, hydroxy substituted and halogen substituted phenyl radicals having 6-26 C; and unsubstituted, alkyl substituted and halogen substituted heterocyclic radicals having 4-15 C; R₂ is selected from the group consisting of hydrogen, alkyl radicals having 1-12 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-20 C, halogen substituted alkyl radical having 1-12 C; and unsubstituted, alkyl substituted and halogen substituted phenyl radicals; and R₁ and R₂ together with the carbon atom to which they are bonded may form a cycloaliphatic ring selected from the group consisting of unsubstituted and alkyl, phenyl, phenylalkyl, alkylidene and phenylalkylidene substituted cycloaliphatic rings having 5-30 C; R₃ and R₄ are each selected from the group consisting of hydrogen, alkyl radicals having 1-12 C, unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-20 C; unsubstituted, alkyl substituted and halogen substituted phenyl radicals having 6-20 C; halogen substituted alkyl radicals having 1-12 C, and halogen substituted phenylalkyl radicals having 7-20 C; and R₃ and R₄ taken together with the two adjacent carbon atoms to which they are respectively bonded may form a cycloaliphatic ring selected from the group consisting of unsubstituted and alkyl, phenyl, phenylalkyl alkylidene, phenylalkylidene and hydroxy phenylalkylidene substituted cycloaliphatic rings having 5-25 C; R₅ and R₆ are each selected from the group consisting of alkyl radicals having 4-12 C, phenylalkyl radicals having 9-18 C; unsubstituted, alkyl substituted and halogen substituted cycloalkyl radicals having 5-21 C; unsubstituted, alkyl substituted and halogen substituted phenylcycloalkyl radicals having 9-25 C; halogen substituted alkyl radicals having 4-12 C, and halogen substituted phenylalkyl radicals having 9-18 C.
 3. The composition of claim 1 wherein said elastomer is an ethylene/propylene copolymer.
 4. The composition of claim 2 wherein said plastomer is polyethylene.
 5. The composition of claim 1 which comprises between about 0.5 and 10% by weight of said peroxide based on the weight of said elastomer.
 6. The composition of claim 5 wherein said weight percentage of peroxide is between about 2 and 5%.
 7. The composition of claim 2 which comprises between about 0.5 and 10% by weight of said peroxide based on the weight of said plastomer.
 8. The composition of claim 7 wherein said weight percentage of peroxide is between about 2 and 5%.
 9. The composition of claim 5 which comprises about 100 parts by weight of ethylene/propylene copolymer, 10 to 80 parts by weight of carbon black, 1 to 10 parts by weight of ZnO or MgO, and 0.15 to 0.5 parts by weight of sulfur.
 10. A process for vulcanizing the composition of claim 9 which comprises heating said composition at a temperature between about 140°C and 190°C for a time between about 5 and 200 minutes.
 11. The process of claim 10 wherein said vulcanization temperature is between about 150°C and 170°C and said vulcanization time is between about 5 and 15 minutes.
 12. A process for crosslinking the composition of claim 7 which comprises heating said composition at a temperature between about 100°C and 200°C, at a pressure between about 50 and 200 kg/cm² for a time between about 5 and 60 minutes.
 13. The process of claim 12 wherein said crosslinking temperature is between about 145°C and 165°C and said crosslinking time is between about 10 and 30 minutes.
 14. Vulcanized elastomers obtained by the process of claim
 10. 15. Crosslinked plastomers obtained by the process of claim
 12. 